diff --git a/guix-data-service/model/system-test.scm b/guix-data-service/model/system-test.scm
index ab438b7..9bbc228 100644
--- a/guix-data-service/model/system-test.scm
+++ b/guix-data-service/model/system-test.scm
@@ -37,14 +37,15 @@
              conn
              "system_tests"
              '(name description location_id)
-             (map (match-lambda
-                    ((name description derivation-ids-by-system location-data)
-                     (list name
-                           description
-                           (location->location-id
-                            conn
-                            (apply location location-data)))))
-                  system-test-data)))
+             (list->vector
+              (map (match-lambda
+                     ((name description derivation-ids-by-system location-data)
+                      (list name
+                            description
+                            (location->location-id
+                             conn
+                             (apply location location-data)))))
+                   system-test-data))))
            (data
             (append-map
              (lambda (system-test-id derivation-ids-by-system)
@@ -54,7 +55,7 @@
                             (cdr system-and-derivation-id)
                             (car system-and-derivation-id)))
                     derivation-ids-by-system))
-             system-test-ids
+             (vector->list system-test-ids)
              (map third system-test-data))))
 
       (exec-query